Recherche avancée

Sur d’autres sites (7228)

• ffmpeg - duration usage in input text file

  12 mai 2018, par Voicu

  I am trying to use ffmpeg to concatenate video segments with some black screen. To do that I’ve first generated a blank 10-second video (no audio track) with :

  $ ffmpeg -f lavfi -i color=black:s=320x240:r=1 -f lavfi -i anullsrc -t 10 -vcodec libvpx -an blank.mkv

  I then created the simplest possible scenario within input.txt file (contents below) in order to have three seconds of black screen followed by some video (no audio track) :

  file 'blank.mkv'
  
  duration 3
  
  file 'video_example.mkv'

  And, finally, ran the following ffmpeg command to concat the contents of that input file :

  $ ffmpeg -f concat -i input.txt -codec:v copy -codec:a copy output.mkv

  The issue that I have is that the duration 3 is not considered, so the final video still has ten seconds of black frames (instead of three) followed by my video. And also "Non-monotonous DTS in output stream 0:0 ..." message is shown when using duration x in the file. If I remove duration the warnings are gone and getting the 10-second black screen first output as well.

  Full output of the ffmpeg concat command :

  $ ffmpeg -hide_banner -f concat -i input.txt -codec:v copy -codec:a copy output.mkv
  
  Input #0, concat, from 'input.txt':
  
    Duration: N/A, start: 0.000000, bitrate: N/A
  
      Stream #0:0: Video: vp8, yuv420p(progressive), 320x240, SAR 1:1 DAR 4:3, 1 fps, 1 tbr, 1k tbn, 1k tbc
  
      Metadata:
  
        ENCODER         : Lavc57.107.100 libvpx
  
        DURATION        : 00:00:10.000000000
  
  File 'output.mkv' already exists. Overwrite ? [y/N] y
  
  Output #0, matroska, to 'output.mkv':
  
    Metadata:
  
      encoder         : Lavf57.83.100
  
      Stream #0:0: Video: vp8 (VP80 / 0x30385056), yuv420p(progressive), 320x240 [SAR 1:1 DAR 4:3], q=2-31, 1 fps, 1 tbr, 1k tbn, 1k tbc
  
      Metadata:
  
        ENCODER         : Lavc57.107.100 libvpx
  
        DURATION        : 00:00:10.000000000
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (copy)
  
  Press [q] to stop, [?] for help
  
  [concat @ 000000000031a440] DTS 3000 < 9000 out of order
  
  [matroska @ 0000000000328420] Non-monotonous DTS in output stream 0:0; previous: 9000, current: 3000; changing to 9000. This may result in incorrect timestamps in the output file.
  
  [matroska @ 0000000000328420] Non-monotonous DTS in output stream 0:0; previous: 9000, current: 4001; changing to 9000. This may result in incorrect timestamps in the output file.
  
  [matroska @ 0000000000328420] Non-monotonous DTS in output stream 0:0; previous: 9000, current: 4998; changing to 9000. This may result in incorrect timestamps in the output file.
  
  [matroska @ 0000000000328420] Non-monotonous DTS in output stream 0:0; previous: 9000, current: 6004; changing to 9000. This may result in incorrect timestamps in the output file.
  
  [matroska @ 0000000000328420] Non-monotonous DTS in output stream 0:0; previous: 9000, current: 7002; changing to 9000. This may result in incorrect timestamps in the output file.
  
  [matroska @ 0000000000328420] Non-monotonous DTS in output stream 0:0; previous: 9000, current: 8005; changing to 9000. This may result in incorrect timestamps in the output file.
  
  frame= 5794 fps=0.0 q=-1.0 Lsize=    7109kB time=01:37:09.70 bitrate=  10.0kbits/s speed=5.16e+004x
  
  video:7043kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.926229%

  Any idea what am I doing wrong ? The warning seems to hint towards the issue here.

  Other possibly useful info :

  $ ffprobe -hide_banner blank.mkv
  
  Input #0, matroska,webm, from 'blank.mkv':
  
    Metadata:
  
      ENCODER         : Lavf57.83.100
  
    Duration: 00:00:10.00, start: 0.000000, bitrate: 1 kb/s
  
      Stream #0:0: Video: vp8, yuv420p(progressive), 320x240, SAR 1:1 DAR 4:3, 1 fps, 1 tbr, 1k tbn, 1k tbc (default)
  
      Metadata:
  
        ENCODER         : Lavc57.107.100 libvpx
  
        DURATION        : 00:00:10.000000000
  
  
  
  $ ffprobe -hide_banner video_example.mkv
  
  Input #0, matroska,webm, from 'video_example.mkv':
  
    Metadata:
  
      encoder         : GStreamer matroskamux version 1.8.1.1
  
      creation_time   : 2018-05-04T17:57:04.000000Z
  
    Duration: 01:37:08.70, start: 15434.269000, bitrate: 9 kb/s
  
      Stream #0:0(eng): Video: vp8, yuv420p(progressive), 320x240, SAR 1:1 DAR 4:3, 1 fps, 1 tbr, 1k tbn, 1k tbc (default)
  
      Metadata:
  
        title           : Video
  
  
  
  $ ffmpeg -v
  
  ffmpeg version 3.4.2 Copyright (c) 2000-2018 the FFmpeg developers
  
    built with gcc 7.3.0 (GCC)

• FFmpeg - Multiple videos with 4 areas and different play times

  25 mai 2018, par Robert Smith

  I have videos as follows

  video   time
  
  ======= =========
  
  Area 1:
  
  video1a    0-2000
  
  video1b 2500-3000
  
  video1c 3000-4000
  
  
  
  Area 2:
  
  video2a  300- 400
  
  video2b  800- 900
  
  
  
  Area 3:
  
  video3a  400- 500
  
  video3b  700- 855
  
  
  
  Area 4:
  
  video4a  400- 500
  
  video4b  800- 900

  Basically these are security camera outputs and should display in 4 areas :

  So far I have the following :

  ffmpeg
  
      -i 1.avi -i 2.avi -i 3.avi -i 4.avi
  
      -filter_complex "
  
          nullsrc=size=640x480 [base];
  
          [0:v] setpts=PTS-STARTPTS, scale=320x240 [upperleft];
  
          [1:v] setpts=PTS-STARTPTS, scale=320x240 [upperright];
  
          [2:v] setpts=PTS-STARTPTS, scale=320x240 [lowerleft];
  
          [3:v] setpts=PTS-STARTPTS, scale=320x240 [lowerright];
  
          [base][upperleft] overlay=shortest=1 [tmp1];
  
          [tmp1][upperright] overlay=shortest=1:x=320 [tmp2];
  
          [tmp2][lowerleft] overlay=shortest=1:y=240 [tmp3];
  
          [tmp3][lowerright] overlay=shortest=1:x=320:y=240
  
      "
  
      -c:v libx264 output.mp4

  But there are two things I am missing :

  • The above is only for 4 video files, I need a way to add additional files to each area (for example video1b should play at its corresponding time after video1a in the same area)
  • How do I specify the beginning/ending time as shown above for each file ?

• How to check when ffmpeg completes a task ?

  25 mai 2018, par Andrew

  I’m just learning how to use ffmpeg a few hours ago to generate video thumbnails.

  These are some results :

  

  

  I’d used the same size (width - height) to Youtube’s. Each image contains max 25 thumbnails (5x5) with the size 160x90.

  Everything looks good until :

  public async Task GetVideoThumbnailsAsync(string videoPath, string videoId)
  
  {
  
      byte thumbnailWidth = 160;
  
      byte thumbnailHeight = 90;
  
  
  
      string fps = "1/2";
  
  
  
      videoPath = Path.Combine(_environment.WebRootPath, videoPath);
  
  
  
      string videoThumbnailsPath = Path.Combine(_environment.WebRootPath, $"assets/images/video_thumbnails/{videoId}");
  
      string outputImagePath = Path.Combine(videoThumbnailsPath, "item_%d.jpg");
  
  
  
      Directory.CreateDirectory(videoThumbnailsPath);
  
  
  
      using (var ffmpeg = new Process())
  
      {
  
          ffmpeg.StartInfo.Arguments = $" -i {videoPath} -vf fps={fps} -s {thumbnailWidth}x{thumbnailHeight} {outputImagePath}";
  
          ffmpeg.StartInfo.FileName = Path.Combine(_environment.ContentRootPath, "FFmpeg/ffmpeg.exe");
  
          ffmpeg.Start();
  
      }
  
  
  
      await Task.Delay(3000);
  
  
  
      await GenerateThumbnailsAsync(videoThumbnailsPath, videoId);
  
  }

  I’m getting a trouble with the line :

  await Task.Delay(3000);

  When I learn the way to use ffmpeg, they didn’t mention about it. After some hours failed, I notice that :

  An mp4 video (1 min 31 sec - 1.93Mb) requires some delay time 1000ms. And other, an mp4 video (1 min 49 sec - 7.25Mb) requires some delay time 3000ms.

  If I don’t use Task.Delay and try to get all the files immediately, it would return 0 (there was no file in the directory).

  Plus, each file which has a difference length to the others requires a difference delay time. I don’t know how to calculate it.

  And my question is : How to check when the task has completed ?

  P/s : I don’t mean to relate to javascript, but in js, there is something called Promise :

  var promise = new Promise(function (done) {
  
      var todo = function () {
  
          done();
  
      };
  
  
  
      todo();
  
  });
  
  
  
  promise.then(function () {
  
      console.log('DONE...');
  
  });

  I want to edit the code like that.

  Thank you !